An extensive study of tree growth rings says there could be a link between the rise and fall of past civilisations and sudden shifts in Europe's climate.

A team of researchers based their findings on data from 9,000 wooden artifacts from the past 2,500 years.

They found that periods of warm, wet summers coincided with prosperity, while political turmoil occurred during times of climate instability.

The findings have been published online by the journal Science.

"Looking back on 2,500 years, there are examples where climate change impacted human history," co-author Ulf Buntgen, a paleoclimatologist at the Swiss Federal Research Institute for Forest, Snow and Landscape, told the Science website.

Cities and metropolitan regional governments should play a more prominent role in defining the wider response to climate change, according to a new report from the OECD.

Cities and Climate Change confirms that urban areas use most of the world’s energy and are responsible for most of the world’s greenhouse gas emissions. Cities are at the same time highly vulnerable to the rising sea levels, warmer temperatures and destructive storms expected to result from climate change: by 2070, 150 million city-dwellers, producing 9% of global GDP in coastal cities, will be exposed to the full brunt of climate change, according to the report.

Some 15,000 delegates gather at the Mexican resort of Cancun on Monday for an annual UN conference on climate change. Scientists say emissions should be cut 25-40 percent below 1990 levels by 2020 to prevent a dangerous rise in global temperatures.

The disruption may already have begun.

Researchers point to this summer’s historic heat wave in Russia and nationwide floods in Pakistan as portents of things to come. In the Arctic Ocean, the summer melt of the ice cap has reached unprecedented proportions in recent years, and studies suggest the summer ocean may be ice-free as early as this decade.

Here in Mexico, research points to a drying out and shrinking of farm output in some regions, which might lead to a greater exodus of Mexican migrants to the U.S.

The World Bank said Thursday in Nagoya it will begin a project to help developing countries integrate the economic benefits of nature into their state policies in an effort to save millions of people from poverty while making sure their natural assets are used in a sustainable way.